1. Field of the Invention
The present invention generally relates to the art of making cultivation tunnels over seeded rows and more specifically to an apparatus serving to drive wire rod arches into the ground, along and over seeded rows, over which arches sheets of polyethylene or other similar translucent material are thereafter laid to complete the tunnels. These tunnels are of course made to provide favourable conditions for the development of growing seedings, including protection against frost.
2. Description of the Prior Art
In the past, the arches were obtained by first bending straight wire rod lengths and then manually driving them into the ground. The method is of course time consuming and thus expensive.
A search made prior to the drafting of the present specification has been made to determine the possible existence of various proposals at mechanization of the method. The patents found during the search are U.S. Pat. Nos. 3,353,297 to Gervais; 4,492,626 to Hammond and 4,186,520 to Alper et al.
The machine proposed by Gervais serves to lay a continuous protective sheet directly over a row of previously sown plants, seeds or seedlings but is not concerned with building cultivation tunnels and does not therefore use arches. Hammond, on the other hand, uses arches in the making of his tunnel but the invention bears on the particular structure of the arches to ensure firm securing of the plastic sheet over them. Nothing is said of the manner into which the arches are driven or planted into the ground.
Alper et al is however of more interest in that it is directed toward an apparatus for mechanically forming and mounting in position wire arches for the making of a cultivation tunnel. For this purpose, the Alper et al apparatus has a pair of lateral endless belts forming a pair of parallel downwardly inclined lower stretches extending in the direction of movement of the machine. A third endless belt is provided in the middle of the two lateral belts, having an upwardly inclined stretch followed by a downwardly inclined one above which is a fourth endless belt having a lower stretch disposed at a short distance from and parallel to the downwardly inclined stretch of the third belt; the two latter stretches forming a passage to guide the center of a rod being bent and drive it into the ground. The straight rod is first fed, at its center, to the upwardly inclined third belt and while moving up the incline, it is bent in the form of an arch by the stretches of the two lateral belts. As the bent rod reaches the passage between the third and fourth belts, it is moved downward and driven into the ground.
The Alper et al machine has the inconvenience of requiring a large number of drive and driven sprocket wheels of which the driven mechanisms further require additional sprocket wheels. The synchronization of the speeds of all the belts is complicated and yet has to be achieved with a certain accuracy otherwise the arches will not be properly bent and planted into the ground. Also, since there is no positive way of holding the legs of the arches against the two lateral belts, any slipping may also cause ill bending of the arches or faulty planting into the ground.